The long term objectives of this program of research are to increase the usefulness of event-related potentials (ERPs) in cognitive neuroscience and clinical neurophysiology and to investigate issues related to functional localization of sensory, motor, and cognitive processing. The proposed studies emphasize intracranial ERP recording in humans supplemented by scalp recordings taken before and after neurosurgical excisions, and by intracranial recordings in monkeys. Specific aims during the next five years are: 1. To identify ERPs sensitive to visual and somatosensory selective attention, to determine in what brain regions these ERPs are generated, and to characterize their temporal course. ERP evidence for the sequential movement of attention in visual space will be sought. These studies will be carried out in patients with intracranial electrodes placed in relevant sensory cortex, and in normal subjects. 2. To identify ERPs sensitive to semantic and repetition priming, to determine in what brain regions these ERPs are generated, and to examine the effects of attention upon these linguistic processes to determine their degree of automaticity. These studies will also investigate attentional shifts between different channels of linguistic information on the basis of inter-channel priming. 3. To continue our studies of hippocampal ERPs, particularly those which have been associated with scalp-recorded P300 and N400, and to examine the effects of unilateral amygdalo-hippocampectomy. 4. To provide improved ERP techniques for localization of face, trunk, and leg areas of sensorimotor cortex, the second somatosensory area, and supplementary motor and sensory areas during neurosurgery. 5. To provide better understanding of the function of the supplementary motor area, particularly in the initiation and control of voluntary movements including speech-related movement. Movement-related potentials will be recorded from this and from other regions of frontal cortex of chronically implanted patients. 6. To continue application of improved methods for identifying the brain structures and specific cell populations that generate ERPs. Empirical scalp and intracranial potential distributions win be compared with calculated distributions using a realistic model of the shape and conductivity of the human head. The proposed research takes advantage of established clinical collaborations with the Epilepsy Surgery Program of the West Haven VA Medical Center and Yale University School of Medicine in which ERP recordings from the cortical surface and chronically implanted depth electrodes in human patients are obtained. These studies will be augmented by comparable studies in normal human subjects and in non-human primates.